In the manufacture of integrated circuits (IC), or chips, patterns representing different layers of the chip are created by a chip designer. A series of reusable masks, or photomasks, are created from these patterns in order to transfer the respective designs of various chip layers onto a semiconductor substrate during the manufacturing process. Mask pattern generation systems use precision lasers or electron beams to image the design of the layers of the chip onto a respective mask. The masks are then used much like photographic negatives to transfer the circuit patterns for the layers onto a semiconductor substrate. These layers are built up using a sequence of processes and translate into the tiny transistors and electrical circuits comprising the completed chip. Conventionally, devices on semiconductor substrates are manufactured by a sequence of lithographic processing operations for forming the devices from a plurality of overlying layers having individual patterns. Generally, a set of 15 to 100 masks is used to construct a chip, and can be used repeatedly.
Flat panel glass is used as a substrate in the production of displays. Alignment of many patterned features in many layers and process operations is influential to the ultimate pixel size and intended display resolution. Residual stress in the glass inherent to the glass manufacturing process may cause patterns on the glass to move during subsequent processing operations. For example, a thermal operation may relieve either locally or globally the stress in the glass substrate resulting in a pattern misalignment with features formed later in the process flow, thus decreasing the yield of higher resolution displays.